The present invention relates to a polishing composition, and more specifically to a polishing composition that is used in, for example, a polishing step for forming wirings of semiconductor device.
In the process of semiconductor device production, a polishing step has been carried out in accordance with CMP (Chemical Mechanical Polishing). In the wiring forming method in accordance with CMP, wiring trenches are formed on an insulation layer and then a metal layer is formed on the insulation layer so that it fills up the wiring trenches completely. The metal layer is then polished and removed so that the top surface of the insulation layer is exposed. Wiring is formed of the metal layer left in the wiring trenches.
Japanese National Phase Laid-Open Patent Publication No. 2000-501771 discloses a prior art polishing composition. The polishing composition is produced by adding ammonium persulfate, potassium periodate and sodium hydroxide to alumina slurry. The alumina slurry mechanically polishes the metal layer and the synergistic action of ammonium persulfate and potassium periodate improves the polishing rate for the conductive layer.
The composition currently in use, however, enhances not only the polishing rate for the conductive layer, but also the polishing rate for the insulation layer. As a result, when using the polishing composition currently in use to carry out final polishing of the metal layer and the insulation layer in the wiring area, the top surface level of the insulation layer in the wiring area becomes lower than that of the insulation layer outside the wiring area, which means creation of local erosion (refer to FIG. 3).